Document how to perform a GETCONNECTOR ioctl. Document the various
struct fields. Also document how to perform a forced probe, and when
should user-space do it.
Signed-off-by: Simon Ser <contact@xxxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Pekka Paalanen <ppaalanen@xxxxxxxxx>
---
include/uapi/drm/drm_mode.h | 76 ++++++++++++++++++++++++++++++++++---
1 file changed, 71 insertions(+), 5 deletions(-)
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 5ad10ab2a577..cd97c5671c75 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -368,27 +368,93 @@ enum drm_mode_subconnector {
#define DRM_MODE_CONNECTOR_WRITEBACK 18
#define DRM_MODE_CONNECTOR_SPI 19
+/**
+ * struct drm_mode_get_connector - Get connector metadata.
+ *
+ * User-space can perform a GETCONNECTOR ioctl to retrieve information about a
+ * connector. User-space is expected to retrieve encoders, modes and properties
+ * by performing this ioctl at least twice: the first time to retrieve the
+ * number of elements, the second time to retrieve the elements themselves.
+ *
+ * To retrieve the number of elements, set @count_props and @count_encoders to
+ * zero, set @count_modes to 1, and set @modes_ptr to a temporary struct
+ * drm_mode_modeinfo element.
+ *
+ * To retrieve the elements, allocate arrays for @encoders_ptr, @modes_ptr,
+ * @props_ptr and @prop_values_ptr, then set @count_modes, @count_props and
+ * @count_encoders to their capacity.
+ *
+ * Performing the ioctl only twice may be racy: the number of elements may have
+ * changed with a hotplug event in-between the two ioctls. User-space is
+ * expected to retry the last ioctl until the number of elements stabilizes.
+ * The kernel won't fill any array which doesn't have the expected length.
+ *
+ * **Force-probing a connector**
+ *
+ * If the @count_modes field is set to zero, the kernel will perform a forced
+ * probe on the connector to refresh the connector status, modes and EDID.
+ * A forced-probe can be slow and the ioctl will block.
+ *
+ * User-space shouldn't need to force-probe connectors in general: the kernel
+ * will automatically take care of probing connectors that don't support
+ * hot-plug detection when appropriate. However, user-space may force-probe
+ * connectors on user request (e.g. clicking a "Scan connectors" button, or
+ * opening a UI to manage screens).
+ */
struct drm_mode_get_connector {
-
+ /** @encoders_ptr: Pointer to ``__u32`` array of object IDs. */
__u64 encoders_ptr;
+ /** @modes_ptr: Pointer to struct drm_mode_modeinfo array. */
__u64 modes_ptr;
+ /** @props_ptr: Pointer to ``__u32`` array of property IDs. */
__u64 props_ptr;
+ /** @prop_values_ptr: Pointer to ``__u64`` array of property values. */
__u64 prop_values_ptr;
+ /** @count_modes: Number of modes. */
__u32 count_modes;
+ /** @count_props: Number of properties. */
__u32 count_props;
+ /** @count_encoders: Number of encoders. */
__u32 count_encoders;
- __u32 encoder_id; /**< Current Encoder */
- __u32 connector_id; /**< Id */
+ /** @encoder_id: Object ID of the current encoder. */
+ __u32 encoder_id;
+ /** @connector_id: Object ID of the connector. */
+ __u32 connector_id;
+ /**
+ * @connector_type: Type of the connector.
+ *
+ * See DRM_MODE_CONNECTOR_* defines.
+ */
__u32 connector_type;
+ /**
+ * @connector_type_id: Type-specific connector number.
+ *
+ * This is not an object ID. This is a per-type connector number. Each
+ * (type, type_id) combination is unique across all connectors of a DRM
+ * device.
+ */
__u32 connector_type_id;
+ /**
+ * @connection: Status of the connector.
+ *
+ * See enum drm_connector_status.
+ */
__u32 connection;
- __u32 mm_width; /**< width in millimeters */
- __u32 mm_height; /**< height in millimeters */
+ /** @mm_width: Width of the connected sink in millimeters. */
+ __u32 mm_width;
+ /** @mm_height: Height of the connected sink in millimeters. */
+ __u32 mm_height;
+ /**
+ * @subpixel: Subpixel order of the connected sink.
+ *
+ * See enum subpixel_order.
+ */
__u32 subpixel;
+ /** @pad: Padding. */
__u32 pad;
};
--
2.29.2
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